49cc Hiccups?

[panacea]

Hello all, new user here. I have been using mr 49ccscoots youtube Channel for Project TaoTao and this forum to help me TREMENDOUSLY! However, I have run into a new issue I cannot figure out.

I don't know if my autochoke gets power, I will determine that later. On the other hand, it now starts up immediately[YES!!!]. Problem now is that it hiccups when riding. If I keep it low throttle, it will be smooth, but once I go 3/4-WOT, it starts to be like BAAAAA-----AAAAAAA-AAA---AAAAA 

And I can't figure out what that's about. New iridum Spark Plug, Orange Coil, Orange CDI, Performance Carb, 3rd of 5 places on the needle, I know my idle screw is really far out considering the 2.5 turns I was suggested by a local shop, and I've been trying to determine the issue. I'm thinking now it could be too lean?? I may need to raise my needle. I have 2 more spaces to raise it with. 



Also, fun fact, after fixing a few things, I took it for a spin, and suddenly was sputtering, struggling to go 3 mph, just to find out my fuel line came apart. Leaked a good bit of gas all over the road. LOL got that secured and fixed.

[Zino]

if she starts up flawlessly from cold your auto choke is working

3/4 to wot is the main jets area the needle and idle screw have almost no effect there .
your main jet is what i would work on .
try to go up or down a couple of sizes
one way will make it way worse and the other way will start to perform better

[classacted]

I have experimented with that auto choke and found that most of the time, it's not needed. during the summer my bike starts up every time immediately without it. late august through the fall and winter it is needed when the engine is allowed to get cold. I always prefer to try to start without choke first, keeping the spark plug dry, and apply choke as needed.
I think how that enricher/choke works is, it's a timed choke. it always makes a rich mixture go to the engine at immediate startup and gradually leans the mixture out.

[GrumpyUnk]

My guess would be to check fuel supply. If the rubber lines are getting old and starting to crack, a slight crack can reduce vacuum to operate the petcock. Low vacuum could allow the petcock to start to close and cut off fuel supply. The fuel outlet in the tank should be looked at for 'cruds' that collect and start to block the screen outlet. The fuel filter should be checked.
If you disconnect the fuel line from the carburetor, and apply suction to the diaphragm, you should get fuel flow that is the full diameter of the fuel line, without hesitation or dribble, it should be able to drain the tank without any interruption. If not, the above checks apply.
tom

[timwhite74]

GrumpyUnk Can you elaborate on this please, "If you disconnect the fuel line from the carburetor, and apply suction to the diaphragm, you should get fuel flow that is the full diameter of the fuel line, without hesitation or dribble, it should be able to drain the tank without any interruption" because I'm having the same problem as the original poster.
I just got my scooter back from a shop. They had it for 3 weeks and figure out the sputtering, so I took it home.

thank you

[aeroxbud]

Jul 20, 2023 13:54:33 GMT -5 timwhite74 said:

GrumpyUnk Can you elaborate on this please, "If you disconnect the fuel line from the carburetor, and apply suction to the diaphragm, you should get fuel flow that is the full diameter of the fuel line, without hesitation or dribble, it should be able to drain the tank without any interruption" because I'm having the same problem as the original poster.
I just got my scooter back from a shop. They had it for 3 weeks and figure out the sputtering, so I took it home.

thank you

What his is referring to is if you suck on the vacuum line. Fuel should flow out of the fuel line in a stream.

[GrumpyUnk]

Yup. The suction line in question should be attached to the black elbow the carb is clamped onto. The line is likely on the right side with a clamp, goes under the carb and routes back up to the petcock. It pulls on the diaphragm when the engine cranks/runs and develops vacuum. Pulling opens the fuel valve and allows flow from the tank, thru the filter to the carb inlet.
You can disconnect at the elbow, or at the diaphragm, and apply suction. If the vacuum line smells of fuel it may have a leaky diaphragm, and the petcock need to be replaced.
I have used a MityVac to apply vacuum and successfully drained the fuel tank on occasion. A golf tee is a useful tool when fiddling with vacuum and fuel lines. It plugs nicely and stays in place. Wooden tees will not dissolve in fuel.
tom

[timwhite74]

aeroxbud and GrumpyUnk Super helpful! thank you. I hope this fixes my issue. Mine idles strong n smooth but sputters under normal throttle/acceleration especially once the engine gets hot...it's also 105 degrees outside.

[GrumpyUnk]

Have you checked that the accelerator pump shoots a jot if fuel out its port when you open the throttle? There is a flat lever by the linkage that reaches down to the pump and pushes on a shaft when the throttle is opened. I think many are late or slow to start pushing, and need to have the arm adjusted(bending) so the bronze-looking pump shaft is moved as soon as the throttle starts to open.
If your pump link is not moving from the beginning, air will accelerate into the carb QUICKLY but the fuel, being more dense, will take a smidge of time before it can catch up to the airflow. The pump helps by adding some fuel that will keep the engine running smoothly until the fuel flow through all the gizzards will catch up.
Probable cause. As the saying goes.
tom

[timwhite74]

I’ll check that too GrumpyUnk . I’m waiting for a new pet cock to arrive. ANOTHER QUESTION: should the fuel filter always be full? I ran the scooter today, still has hiccups, and while on the stand and hiccuping I gave it gas as if I was riding down the street and noticed the fuel drained out of the filter, filled halfway with fuel, drained, and filled half with fuel again. I don’t know if that means anything.
Thanks

[classacted]

the fuel filter from my bike is never totally full of fuel. there is always SOME air in there and it's been running flawlessly for at least 9 months now.

[GrumpyUnk]

If the filter is fill-drain-fill-drain... I would think about a sticking float valve. If the valve stuck closed, the filter would refill and as soon as the float valve opened, it would drain the filter into the float bowl. Rinse repeat.
OTOH, if the outlet is a bit clogged, with the vacuum petcock wide open, the flow may be restricted or intermittent... Your choice.
My impression is that if the petcock is open(vacuum applied) the fuel should flow out of the fuel line as full diameter as long as there is fuel in the tank. If it won't, either the outlet or the petcock or the filter or the fuel line may have some blockage.
tom

[timwhite74]

classacted and GrumpyUnk thank you, I have a brand new carb on it, but I'll still check the float valve. classacted Does your fuel filter go completely empty while the engine is running?

[classacted]

never. it has a small air bubble because of the angle it sits at.
remember, my fuel system is totally gravity feed with no vacuum petcock. just a high up gas tank behind my back, fuel line, filter, and carb. if you have a fuel pump AND a vacuum petcock, then you may NEED to pay attention to your fuel filter, because it is showing the availability of fuel and if you're lucky, movement as well.

[GrumpyUnk]

I have yet to see a filter that is totally full of fuel. As far as I have seen, they all have a trapped air bubble. I suppose it could be removed/filled by disconnecting at the petecock to allow air out, and allow fuel in. As long as there is enough fuel to cover the OUTLET feeding the carb, the float bowl would never see air.
tom